Unit 1- Protein Control of Cell Division

Question 1

Describe the cytoskeleton.

Answer 1

Gives shape and mechanical support to cells. Consists of microtubules.

Question 2

What are microtubules?

Answer 2

Hollow, straight cylinders composed of tubulins. Radiate from the microtubule organising centre or centrosome.

Question 3

Describe the cell cycle.

Answer 3

Interphase, Mitotic phase.

Question 4

Describe the interphase.

Answer 4

G1- growth of proteins and organelles.
S - DNA is replicated.
G2 - further growth phase.

Question 5

Describe the mitotic phase.

Answer 5

Mitosis (PMAT) AND cytokinesis.

Question 6

Describe the prophase (PMAT).

Answer 6

DNA condensed into chromosomes each of 2 sister chromatids. Nuclear membrane breaks down. Spindle microtubules extend from MTOC and attach to kinetochores of centromere of chromosomes.

Question 7

Describe the metaphase. (PMAT)

Answer 7

Chromosomes are aligned at the metaphase plate.

Question 8

Describe the anaphase. (PMAT)

Answer 8

Spindle microtubules shorten by depolymerisation, chromatids are separated and chromosomes are pulled to opposite poles of the cell.

Question 9

Describe the telophase. (PMAT)

Answer 9

The chromosomes decondense and nuclear membranes form around them.

Question 10

Describe cytokinesis.

Answer 10

Comes after mitosis, the cytoplasm is separated into two daughter cells.

Question 11

What are checkpoints in the cell cycle?

Answer 11

Mechanisms which halt and assess the condition of the cell before progressing through cycle.

G1, G2, M.

Question 12

Describe the role of cyclins and CDKs.

Answer 12

Cyclins combine and activate CDKs. Active CDKs phosphorylate proteins that regulate progression through the cell cycle. Sufficient phosphorylation allows progression.

Question 13

What is retinoblastoma protein?

Answer 13

A tumour suppressor that inhibits the transcription of proteins of genes that code for proteins needed for DNA replication. At the G1 checkpoint.

Question 14

Describe the relationship between CDKs and Rb at the G1 checkpoint.

Answer 14

G1 CDKs phosphorylate the Rb. Phosphorylation inhibits Rb, allowing transcription of genes that code for proteins needed for DNA replication.

Question 15

Describe the G2 checkpoint.

Answer 15

DNA replication and damage is assessed. DNA damage triggers activation of protein p53 which can: stimulate DNA repair, arrest cell cycle or induce apoptosis.

Question 16

Describe the M checkpoint.

Answer 16

Progression is halted until the chromosomes are aligned on the metaphase plate and attached to spindle microtubules.

Question 17

An uncontrolled reduction in cell cycle rate could cause what?

Answer 17

A degenerative disease, eg. Alzheimer’s.

Question 18

An uncontrolled increase in cell cycle rate could cause what?

Answer 18

Tumour formation.

Question 19

What is Proto-oncogene?

Answer 19

A gene involved in the control of cell growth or division which can mutate to form a tumour promoting oncogene.

Question 20

Describe apoptosis.

Answer 20

Cell destruction triggered by external or internal death signals.

Question 21

Describe external death signals.

Answer 21

Molecules bind to a surface receptor protein and trigger a protein cascade in the cytoplasm. Eg. Signals from lymphocytes.

Question 22

Describe internal death signals.

Answer 22

A signal resulting from DNA damage causes activation of p53 protein.